Preparation of highly chemically reactive carbon is described in U.S. Pat. No. 1,352,162. The process disclosed provides for the conversion of carbon monoxide to carbon dioxide over a finely divided metal catalyst such as iron, manganese, nickel or cobalt and the like in the virtual absence of air at atmospheric pressure and temperatures of below 700.degree. C. During the conversion, carbon is precipitated upon the catalyst which can be separately collected from the latter by mechanical or magnetic means. The carbon so formed is said to be ashless, highly pure and reactive and suitable for nitrogen fixation processes.
U.S. Pat. No. 1,838,577 is directed toward a process for removal of only traces of oxides of nitrogen together with noxious reactive hydrocarbons from coke oven gas by passing the gas through a filter containing an adsorptive medium. The adsorptive medium is active carbon, the catalytic effect of which is said to be increased by impregnation with metals or metal salts. The patentee further discloses that other materials, such as silica gel, can be employed in lieu of active carbon.
Lastly, U.S. Pat. No. 4,060,589 discloses a process for simultaneously reducing NO.sub.x and SO.sub.x components from stack gases by passing the stack gases over bituminous coke at temperatures between 482.degree. C. and 871.degree. C. Water vapor in the stack gases is said to react with the coke to produce carbon monoxide and hydrogen, the former reacting with the NO.sub.x and the latter reacting with the SO.sub.2. The patentees state that although the conversion is not believed to be effected by catalytic means, the coke may contain specific metals, such as iron, which may accelerate the reductions. The process does appear to be operable on SO.sub.x and some of the NO.sub.x present, both of which were present in trace amounts in a synthetic stack gas employed in the examples.
Although the process of the present invention employs carbon, the carbon does not function as an adsorbant, but chemically reacts with the oxides of nitrogen present to form nitrogen gas. To be useful, such a process should be capable of converting large amounts of nitrogen oxides, not just traces, and at temperatures that are not exceedingly high.